1. Field of the Invention
The present invention generally relates to an optical disc recording apparatus and, more particularly, to an optical disc recording apparatus which records information on a rewritable optical disc such as a CD-RW.
2. Description of the Related Art
A minimum unit for reproduction of information recorded on a recording area of an optical disc such as a compact disc (CD), a recordable optical disc (CD-R) or a rewritable optical disc (CD-RW) is defined as a block of a recording area. Each block can contain information of about 2,048 to 2,352 bytes.
A minimum unit for recording information on an optical disc such as a CD-R or a CD-RW is defined as a packet. Each packet comprises at least one user data block, five link blocks preceding the user data block and two link blocks subsequent to the user data block. The five link blocks preceding the user data block include one link block and four run-in blocks. The two link blocks subsequent to the user data block include two run-out blocks.
As specified in the Orange Book, the link blocks are required for interconnecting a plurality of packets when information is recorded on an optical disc. The link block does not contain user data. It should be noted that a rule for recording data on an optical disc is referred to as a "linking rule".
There are two methods for recording data on an optical disc such as a CD-R (may be referred to as a "recordable compact disc") or a CD-RW (may be referred to as a "rewritable compact disc"). One of the methods is referred to as a "track at-once method" and the other is referred to as a "packet write method".
The track at-once method is for recording information on a track all at one time by using a single packet. The user data blocks in the track are consecutive, and there are no link block between the user data blocks. A single track constitutes a recording unit, and ninety-nine tracks can be formed on the optical disc at maximum. A start address and an end address of each track are recorded on a separate area of the optical disc as a "table of contents (TOC)".
On the other hand, the packet write method is for recording information on a track by dividing the track into a plurality of packets so that the information is recorded on an individual packet basis. Since this method records information by each individual packet, each user data block is discretely located in a single track and link blocks are provided between adjacent ones of user data blocks.
The packet write method is classified into two types, that is, a "fixed packet write method" and a "variable packet write method". In the fixed packet write method, a number of user data blocks within a track is set to a fixed number. The number of user data blocks within a packet is referred to as a packet length or packet size. On the other hand, in the variable packet write method, packets having various packet lengths are provided in a single track.
Additionally, an address (hereinafter referred to as a physical address) is assigned to each block on an optical disc in an ascending order starting from zero "0". The physical address can be accessed by an address (hereinafter referred to as a logical address) which is logically converted from the physical address.
In the variable packet write method, the physical address is linearly related to the logical address, such that the logical address is also assigned to each link block. Accordingly, there exists logical addresses which cannot be accessed.
On the other hand, in the fixed packet write method, the logical address is assigned to only a user data block. That is, each link block is not provided with the physical address so that the physical address is provided to each user data block in a consecutively ascending order. Thus, a physical address of a user data block located at the beginning of a track conforms to the logical address. Accordingly, there is an advantage in that the logical address space is continuous, and information recorded on an optical disc can be reproduced without considering the packet structure of the data to be reproduced.
However, in the above-mentioned fixed packet write method, information must be recorded by a packet having a previously fixed length. That is, a start address and an end address of each packet must conform to a start address and an end address of information to be recorded, respectively. Accordingly, when information to be recorded has a length shorter than a length of each packet, fill data must be added to the information so as to adjust the length of the information to be equal to the length of the entire packet.
Accordingly, when information having a short length is frequently overwritten on a rewritable optical disc by the fixed packet write method, a large amount of meaningless data is recorded on a recording area. Thus, there is a problem in that a large part of the recording area which is provided for recording the user data is wasted, resulting in an inefficient use of the recording area of the optical disc.